This invention relates to a surgeons tool for drilling a hole into an orbital implant for purposes of fixing an artificial eye.
When patients have an eye removed (enucleation or evisceration), an implant is placed into the socket to provide a base for extraocular muscle reattachment. In addition to cosmetic considerations, in younger patients an implant is also essential for appropriate socket growth. At a later date, a prosthesis painted to match the fellow eye is situated in the socket overriding the previously placed implant. It is important that the prosthetic movement match that of the fellow eye to minimize awareness by others that an artificial eye is present. Motility of the prosthesis is usually accomplished by reattaching the eye muscles to the buried implant that is placed first. This allows the socket tissues to move somewhat and the socket movement is partially translated to the prosthesis to move it as well.
Translation of motion between the socket and prosthesis is inefficient unless the system is integrated by some sort of connecting system between the prosthesis and the implant. Unfortunately, most of the early integrated implants were deemed unsatisfactory over the years because many of them became infected or extruded, necessitating removal. The hydroxyapatite implant is an integrated implant but because of its biocompatibility and biointegratability should have a lower rate of infection or extrusion than previous integrated implants. The hydroxyapatite implant is a microporous, corraline sphere which is covered by cadaver donor Eye Bank sclera to which the extraocular muscles are attached. The implant later becomes vascularized from the ingrowth of the host body tissues through its microporous structure. In several months when the implant is completely vascularized, it is drilled for placement of a peg that will later drive an overlying prosthesis.
Drilling the implant correctly can be difficult. It is imperative that the hole be properly positioned to maximize the even distribution of motility in all directions. The prosthesis will be contoured on its posterior aspect to accept the ball-shaped peg head, therefore, the peg must be so positioned to allow the prosthesis to be contoured in an area of sufficient bulk to accommodate the peg. The angulation of the hole is also important in that the peg should be presented perpendicular to the facial frontal plane. This also enhances motility and prevents peg slippage, since the ball is fitting perfectly into the posterior cavity of the prosthesis. Prior to this invention, the hole has been drilled free-handedly. There have been difficulties with maintaining orientation and depth of the drilling. When the drill touches the implant, it bobs within the socket as there is no fixation of the prosthesis to the socket tissue, except for the attached extraocular muscles. The drill may also slip off the hydroxyapatite implant during the drilling procedure and damage the surrounding socket tissue.
This invention is a drill guide that fixates the implant for drilling and also regulates the drilling depth. The drill guide incorporates contoured inserts which enable a variety of different drill designs to be employed. The drill guide is located over the implant and includes fixation features for supporting the implant during the drilling procedure. The device further allows consistent drilling to a predetermined depth and establishes a proper angular positioning of the drilled hole. The use of the device reduces conjunctival trauma, eliminates a need for a surgical assistant, and by encasing the drill, provides protection to the patient as compared with free-handed methods. Moreover, overall surgical time using the drill guide of this invention is decreased.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.